IR 05000336/1979021
| ML19260A660 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/24/1979 |
| From: | Sanders W, Lester Tripp NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML19260A658 | List: |
| References | |
| 50-336-79-21, TAC-11793, NUDOCS 7912030056 | |
| Download: ML19260A660 (7) | |
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U. S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
REGION I
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Report No.
50-336/79-21 Docket No.
50-336 License No.
DPR-65 Priority Category C
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Licensee:
Northeast Nuclear Energy Company P. O. Box 270 Hartford, Connecticut 06101 Facility Name:
Millstone Point 2 Inspection At:
Waterford, Connecticut Inspection Conducted:
August 14-17, 1979 and September 10-12, 1979 Inspectors:
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M. a e /ppf W. F. Sanders, Reactor Inspector t/
date'
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date date Approved by:
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A pd f I[79 f.. E. Triph4 Chief, Engineering Support, date RC&ES Branch Inspection Summary:
Inspection on August 14-17 and September 10-12, 1979 (Report No. 50-336/79-21)
Areas Inspected:
Routine, unannounced inspection by one regional based inspector of the quality control activities related to the repair of the steam line to auxi-liary feedwater pumps and non-destructive examinations of the feedwater nozzles required by Bulletin 79-13.
The inspection involved 36 inspector-hours by one NRC regional based inspector.
Results: No items of noncompliance were identified.
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Region I Form 12 (Rev. April 1977)
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DETAILS 1.
Persons Contacted Principal Licensee Employees
- E. Farrell, Superintendent, Unit 2 J. Opeka, Station Superintendent
- R. Rothgeb, Engineer R. Michaud, Supervisor Construction QC
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E. Debarba, Generation Mechanical Engineer M. Kupinski, Generation Senior Engineer
- J. Kelley, Senior Operator, Acting Superintendent P. Watson, ISI Coordinator U. S. Nuclear Regulatory Commission
- T. Shedlosky, Resident Inspector Crouse Nuclear Energy Services W. Smith, Assistant Superintendent - Site D. Holmes, Senior Technical Engineer Hartford Inspection and Insurance Company R. Smith, Authorized Inspector 2.
General This inspection trip was made to inspect the repairs in progress on the 4" steam supply line to a turbine driven auxiliary feedwater pump and to inspect the non-destructive examinations being performed on the two steam generator nozzles as required by IE Bulletin 79-13.
3.
Steam Generator Feedwater Nozzles During an unscheduled plant shutdown that started on August 9, 1979 for the purpose of repairing a leak in a 4" steam line to an auxiliary feedwater pump, a decision was made by the licensee to inspect the two feedwater nozzles as required by IE Bulletin 79-13.
The welds in two nozzles:
AC-G1 - No. 1 Steam Generator - Nozzle to Safe End BC-G1 - No. 2 Steam Generator - Nozzle to Safe End were examined by radiography using a thru-wall technique and a procedure which was slightly more sensitive than used in the original construction.
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Construction Requirement Present Kodak AA Film / Speed 204 Kodak T - Speed 117 4T Essential Penetrameter Hole 2T Essential Penetrameter Hole The radiography of these two welds detected the presence of several linear indications on or near the heat affected zones of the nozzle safe end to pipe welds which then required the same inspection to be performed on all of the piping welds up to the first piping support in accordance with paragraph 1.b of IE Bulletin 79-13.
The radiography of these welds BC-G2 & AC-G1, which join the first length of straight pipe to the first elbow outside of the concrete shield revealed the presence of additional linear indications.
Since all of the indications were similar in nature to the cracks found in seven Westinghouse plants over the past few months, the licensee requested the assistance of Westinghouse in characterizing and evaluating the indications.
This was done by a review of the con-struction radiographs and comparing to the recent film and subsequently mapping and characterizing and measuring the indications using an ultra-sonic technique and procedure developed by Westinghouse.
The largest flaws were confirmed by ultrasonic and radiography correlations to be cracks with the greatest depth measured at.110 x 6" Lg located inside adjacent to the safe end to pipe weld on the safe end side.
This was in the No. 2 generator; however, other cracks of lesser size were found in both steam generators.
It was noted that the nozzle to safe end and safe end to pipe welds of both steam generators are located within a 24" diameter pipe sleeve which extends approximately five feet through the steam generator shield wall.
The safe end to pipe weld is located 6" inside of the shield wall.
No items of noncompliance were identified with the inspections.
4.
Ultrasonic Inspection A review was made of the ultrasonic test procedure for mapping the radio-graphic indications.
The procedure utilized an ultrasonic flaw detection instrument of the pulse echo type A scan presentation and qualified to the requirements of Westinghouse procedure NSD-ISI-10.
The search unit used was a 60 shear wave with a 2.25 MHz inch diameter transducer.
The IIW block was used for the. basic calibration and to check the operating characteristics of the test system. The Calibration Block identified as TVA7 is a 10 inch x 5 inch x approximately 1 inch thick section of SA 508 riass 2 material containing two ELOX. notches, one notch 1/2 inch.long x 1/16 inch deep and the other notch 1/2 inch long x 1/8 inch deep used to establish a DAC line. The scanning was then done with the search unit on 1464 404
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the safe end, sound beam directed toward the safe end to pipe weld. The search unit was moved to and from the welds on %" increments around the pipe from the 9 o' clock position through the 12 o' clock to 3 o' clock.
This inspection confirmed the location and extent of the sharpest indi-cation c'etected by radiographic techniques.
The record of the size and location of the flaws were reviewed.
No items of noncompliance were identified with this ineectio:.
5.
Meeting in Bethesda August 21, 1979 A meeting with NRR was requested by the licensee to present the total picture of inspection activities and results and to present a proposal to justify continued operation of the plant.
Westinghouse and NNECo gave a combined presentation which consisted of:
a.
Plant Status b.
Piping Layout c.
RT Results d.
UT Results e.
Operational History of Feedwater System f.
Industry Experience on Cracking g.
Evaluation of Worst Case by Fracture Analysis h.
NNECo Proposal for Continued Operation On August 25, 1979, NRR approved by letter and attached Safety Evaluation, the interim operation of the plant until October 31, 1979 based on the following commitments.
1.
Install monitoring equipment for temperature and stress measurements on the steam generator no. 2 feedwater line.
2.
Establish action points on-site and off-site acceptance criteria as presented in the August 24, 1979 letter for initiating controlled plant shutdown if the limits are exceeded.
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3.
Initiate a controlled shutdown to perform an ultrasonic examination of the most severe indications on the affected lines in the event of a feedwater flow instability (water-hammer).
4.
By October 1, 1979, submit a thorough program for repairing the affected welds.
The program will address the modifications required in the steam generator shield wall section.
5.
By October 31, 1979, commence an approach to cold shutdown to perform ultrasonic examination of the four affected welds using the same methods, techniques and conditions as was used to previously charac-terize the indications.
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6.
Prior to startup, install local leak monitoring aquipment capable of detecting a 0.5 gallon / minute leak on both steam generator loops in the vicinity of the cracks.
7.
Initiate a controlled shutdown and inspect the affected welds should combine dynamic stress greater than 40 ksi be measured by the on-site monitoring equipment.
No items of noncompliance were identified.
6.
Instrumentation of Feedwater Nozzles and Piping Prior to plant startup, strain gages (16), thermocouples (10) and Piezoelectric Accelerometers (3) were installed to obtain data to characterize the dynamic response temperature distribution of the feedwater piping due to the varaus operational modes of the feedwater systems.
An inspection was made of the test procedure which has diagrams for the attachment and location of the various equipment.
In addition, the procedure included instructions for the attachment and location of acoustic leak detection of a leak at a distance by the system being sensitive to acoustic signals which are generated when pressurized water escapes through a metal crack.
The inspector noted that (2) acoustical sensors were installed on the no.
2 steam generator and (1) sensor installed on no.1 steam generator FW Nozzles.
No items of noncompliance were identified.
7.
Steam Line Repairs During plant operation a break was observed on a 4" steam line which supplies a turbine driven auxiliary feedwater pump.
The break occurred at a location where a 4" weldolet is welded to the 12" steam dump line and could not be isolated.
This made it necessary to shut the plant down to make the repairs.
The repair was made by removing approximately two feet of the 12" schedule 60 steam dump piping containing a crack in the weld joining the weldolet to the pipe.
A visual irgection shows the crack to be located on or near the heat affected 2one at the toe of the weld where it joins the 12" pipe.
It appeared that the crack initiated at the heat affected zone and propagated downward in an angular direction to the inside of the pipe resulting in a thru-wall fracture of approximately 6" long.
The inspector was informed that the section containing the crack would be sent to a metallurgical laboratory for examination to determine the fracture mechanism.
In addition, changes have been made in the operation of the system to frequently blow the line down in an effort to reduce loading.
The NRC resident inspector is inspecting the operational char-acteristics.
No items of noncompliance were identified.
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8.
Visual Inspection A visual inspection was made of the piping system and the welding activities in progress on the 12" circumferential seams of the replacement section.
The welding was completed which limited the inspection to observations of the weld bead tie in and general weld contour and surface conditiuns.
No items of noncompliance were identified.
9.
Procedures and Records A review was made of the procedures listed below.
a.
Peabody Radiography Procedure 3.20 A 1-3, written for compliance to the requirements of ASME Section V Winter 1976 Addenda b.
Liquid Penetrant CP 126, Revision 2, Crouse Nuclear Energy Service, written to comply with ASME Sections III, V, VIII and XI 1977 to Winter 1978 c.
Procedure Qualification, the above procedure 110-CG-LP-1-PS d.
Weld Procedure - Crouse C-47, Revision 3 e.
Weld Procedure Qualification Record, J. G. Sylvester Associates No.
4787-GTAW and SMAW f.
Weldor Performance Qualification Records for four weldors:
Weldors Symbol M-8 Weldors Symbol M-1 Weldors Symbol M-2 Weldors Symbol M-6 g.
Dye Penetrant Records for four of the new replacement welds, inspected to the procedure referenced in part b of this paragrapit. Also review was made of the records for 12 original welds in tnis system.
h.
Review of randomly selected radiographs of the two 12" replacement welds and three of the 4" replacement welds for compliance to the requirements of the specification referenced in section a and to the requirement of 1976 Edition of ASME Section V
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No items of noncompliance were identified.
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9.
Exit Interview The inspector met with the licensee representatives listed in paragraph 1 at the conclusion of the inspection on September 12, 1979.
The inspector summarized the scope and findings of this inspection.
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